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Winter Weather Forecast Discussion
 
(Caution: Version displayed is not the latest version. - Issued 0908Z Feb 24, 2018)
 
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Abbreviations and acronyms used in this product
 
Geographic Boundaries -  Map 1: Color  Black/White       Map 2: Color  Black/White


PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
408 AM EST SAT FEB 24 2018

VALID 12Z SAT FEB 24 2018 - 12Z TUE FEB 27 2018


...CENTRAL PLAINS TO UPPER MS VALLEY/UPPER GREAT LAKES...

A QUICK HITTING WINTER STORM IS EXPECTED TO LIFT THROUGH THE
CENTRAL PLAINS AND UPPER MS VALLEY/GREAT LAKES ON SAT INTO SUN
MORNING. DYNAMIC SHORT WAVE TROUGH MOVING THROUGH THE FOUR CORNERS
REGION IS EXPECTED TO EJECT OUT INTO THE PLAINS AND SWEEP UP
THROUGH THE UPPER MS VALLEY WITH A SLIGHT NEG TILT. THIS SHOULD
ALLOW A SURFACE WAVE TO DEVELOP AND DEEPEN RAPIDLY OVER THE 24 HR
FORECAST PERIOD, BASICALLY TRANSITIONING THROUGH CYCLOGENESIS. THE
EXTREMELY CLOSE GFS AND ECMWF MODELS HAVE A SURFACE LOW JUST WEST
OF STL BY 00Z/25 BEFORE DEEPENING OVER THE NEXT 12 HRS BY AOA 15
MB, WHILE REACHING THE UP OF MI. THE 00Z NAM APPEARS TO BE A
SLIGHTLY WEAKER OUTLIER WITH A MORE WESTWARD TRACK WITH THE
SURFACE LOW. EXPECT A SWATH OF SNOW ON THE BACKSIDE OF THE SYSTEM
WHERE A HEALTHY DEFORMATION ZONE/COMMA HEAD SHOULD RESULT IN SOLID
ACCUMULATIONS FROM NORTHERN IA THROUGH EASTERN/SERN MN AND
NORTHERN WI AND THE WESTERN PORTION OF THE UP OF MI, WHICH
INCLUDES THE MSP/STP METRO AREAS.

...PACIFIC NORTHWEST/NORTHERN ROCKIES/GREAT BASIN...

A ONE-TWO PUNCH FROM TWO STRONG SHORT WAVE TROUGHS WILL IMPACT
PARTS OF THE WEST THIS WEEKEND WITH HEAVY SNOWFALL, WITH THE
LATTER BEING AN EXTREMELY COLD AMPLIFIED FEATURE. A SHORT WAVE
ALREADY ARRIVING INTO THE PAC NW THIS MORNING WILL SLIDE SOUTH AND
EAST ON SAT THROUGH THE INTER-MOUNTAIN WEST. THE COMBINATION OF
STEADY HEIGHT FALLS AND MODEST PAC MOISTURE TRANSPORT SHOULD
RESULT IN DECENT HEAVY SNOW ACCUMULATIONS FROM THE WA/OR CASCADES
TO THE TETONS/WASATCH AND CO ROCKIES.

THE NEXT POTENT JET STREAK WILL BEGIN REACHING THE PAC NW LATE SAT
INTO SUN, AS THE DIGGING UPPER JET AND NOSE OF INTENSE ONSHORE
FLOW AND VERTICAL LIFT TAKE AIM FOR THE NWRN QUAD OF THE COUNTRY.
THE ANOMALOUS, WELL BELOW AVG HEIGHTS WILL CRASH ACROSS THE REGION
TO YIELD NOT ONLY HEAVY OROGRAPHIC SNOWFALL ACROSS THE TERRAIN BUT
BEGIN TO POTENTIALLY ALLOW SNOWFALL ACCUMULATIONS IN MORE LOW
LYING AND METROPOLITAN AREAS. BY THE END OF SUN, THE WA/OR
CASCADES MAY VERY WELL REACH 2 TO 3 FEET.

FINALLY ON MON, THIS AMPLIFIED UPPER TROUGH WILL DIG DOWN THE REST
OF THE WEST COAST WITH A CLOSED MID TO UPPER LOW DROPPING DOWN THE
NORTHERN/CENTRAL CA COASTLINE. THE COMBINATION OF THE STILL ACTIVE
UPPER JET AND BROAD SWRLY FLOW AHEAD OF THE SYSTEM SHOULD BE
SUFFICIENT FOR SNOWFALL FROM THE NORTHERN CA MTNS AND ENTIRE
SIERRA INTO THE MTNS OF SOUTHERN CA, WHILE SNOW WILL BE COMMON
DOWNSTREAM FROM NV THROUGH NORTHERN UT INTO WESTERN WY.

...INTERIOR NEW YORK AND CENTRAL/NORTHERN NEW ENGLAND...

A COMBINATION OF HEAVY SNOW AND ICING IS ANTICIPATED THIS WEEKEND
ACROSS INTERIOR NEW YORK AND A LARGE PORTION OF NEW ENGLAND. THE
ACTION ON SAT WILL BE A BIT MORE LIMITED AND CONCENTRATED, AS A
FRONTAL ZONE PASSES THROUGH BEFORE LARGE SCALE WARM ADVECTION
ARRIVES FROM THE PENDING STORM UPSTREAM. A SWATH OF MOISTURE WILL
SURGE INTO NEW ENGLAND ON SUN, AS RETREATING WEDGING HIGH PRESSURE
ATTEMPTS TO HOLD ON. THIS WILL RESULT IN A COMBINATION OF ICING
AND SNOW. WPC GENERALLY FOLLOWED A BLEND OF THE GFS/ECMWF FOR
THERMALS OVER THE WEEKEND.


MUSHER